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    Introduction to Ball Valves: General & Technical Details

    1. General Introduction to Ball Valves

    As a species of plug valve, the ball valve is a quarter turn, straight-through flow valve with a spherical ball-shaped closure member. Ball valves are widely used in gas, compressed air, liquid and non-abrasive slurry services as well as vacuum and cryogenic services. Because of the wiping rotary motion of the closure member, ball valves are ideal for non-abrasive slurry services or processes with particulates, since the ball port has a tendency to separate or shear the particulates upon closing movement. 

    According to the operation methods, ball valves can be categorized as manual ball valves and actuated ball valves. Manual ball valves can be either lever operated or worm gear operated that are best suited for stopping and starting flow (on-off service) and moderate throttling. Manual ball valves are typically found in sizes up to 12” (DN300) and in low pressure ratings Class 150 (PN20) through Class 600(PN100). Actuated ball valves can be further classified as pneumatic, electrical and hydraulic operation types based on its actuator’s driving method.

    2. Design Standards and Applicable Range of Ball Valves

    ISO 7121
    Steel ball valves for general 
    purpose industrial applications
    DN15 ~ DN400
    1.0 ~ 10 MPa
    MSS SP 72
    Ball Valves with Flanged or 
    Butt-Welding Ends for General 
    DN15 ~ DN900
    Class 150 ~ Class 900
    API 6D
    Specification for Pipeline Valves
    DN50 ~ DN900
    Class 150 ~ Class 2500
    Oil & Gas Pipeline
    JPI 7S 48
    Steel Flange Ball Valves
    DN15 ~ DN350
    Class 150 ~ Class 300
    Oil & Gas Pipeline
    BS 5351
    Steel Ball Valves for the Petroleum,
    Petrochemical and Allied Industries
    DN8 ~ DN400
    Class 150 ~ Class 800
    Petroleum & 
    Petro Chemical
    BS 5159
    Cast Iron and Carbon Steel Ball 
    Valves for General Purposes
    DN10 ~ DN600
    1.0 ~ 10 MPa
    ASME B16.34
    Valves - Flanged, Threaded, and 
    Welding End
    DN3 ~ DN1300
    Class 150 ~ Class 4500
    API 608
    Metal Ball Valves - Flanged, 
    Threaded and Welding Ends
    DN15 ~ DN600
    Class 150 ~ Class 600
    MSS SP 110
    Ball Valves Threaded, Socket-
    Welding, Solder Joint, Grooved 
    and Flared Ends
    1/4" ~ 4"
    1000 psig ~ 2000 psig
    AWWA C507
    Ball Valves, 6 in Through 48 in (150 
    mm Through 1200 mm)
    6" ~ 48"
    Class 150 ~ Class 300
    Water Supply

    3. Advantages VS. Disadvantages of Using Ball Valves

    1) Advantages: ball valves can provide perfect sealing achieving bubble tight or “zero-leakage”. The opening  & closing stroke can be completed in a very short time hence provides a quick response in On-Off service. The ball vales are not only lighter in weight and smaller in size than a peer gate or globe valve but also require smaller torque to operate. Ball valves have excellent performances in severe services such as high temperature, high pressure, cryogenic service, harsh acid & alkali corrosion and sea water environment.

    2) Disadvantages: ball valves are not suitable for sustained throttling service. If the valve is partially open for an extended period under conditions of a high pressure drop across the ball, the soft seat(usually PTFE) may tend to flow around the edge of the ball orifice and possibly lock the ball in that position. And also in slurry applications, the suspended particles may settle and become trapped in valve body cavities  causing wear, leakage or valve failure.
                                Introduction to Ball Valves: Materials
                                Introduction to Ball Valves: Construction 

    Views:   Author:hbmetals  Date:15/04/02